Oxidation of cresols.



To all whom it may concern:

masnnro rename, or retain, rrALY. Y,

/ i ox'ma'rron oronnsons. I J W PatentedfiMayt, 1 918. Application filed au ust 20,1917. sriaizt isaaec.

No Drawing.

Be it known that 1,. UMBERTO technical chemist, a subject of the King of Italy, residing at 20 Via Melezet, Turin, in

the Kingdomof Italy, have invented cer-' tain new and useful Improvements in or Belating to the Oxidation of Cresols; and I do hereby declare the following to be a'full, clear, andexact description of the invention, such as will enable others skilled in the.

art to which it appertainsto make and use the same.

This invention relates to the oxidation of cresols for the purpose of obtaining the cor-. responding oxyacids or their salts, and more especially for the production of salicylic acid, the chief object of the invention be ing to utilize an electrolytic method so as to obtain a pure product at a substantial reduction in cost as compared with the chemical methods hitherto employed.

It has been proposed to effect the direct conversion of cresols into the corresponding oxyacids bythe fusion of.-the cresols with caustic alkali and certain metallic oxids at high temperatures, but the reactions are practicable only with a large excess of both the alkali and the metallic oxids, found that the metallic oxids and a very large excess of alkali are both unnecessary if an electrolytic method is employed and according to my invention I electrolize a fused mixture of cresol and caustic alkali so that the oxygen liberated at the anode is absorbed and serves for oxidation of the cresol, while the cathodic hydrogen is set free.

The anodes may be of copper, lead, nickel, iron, steel, nickel steel or other suitable metal, nickel, nickel steel and iron especially being unaffected by the combined action of the current and the alkali. A suitable current density is found to be about 5 to 8 amperes per square decimeter, and the mixture may be heated to a temperature of between 200 and 270 0., the first figure being considerably lower than that necessary for the chemical oxidation referred to.

- The following is given as a typical example of a method of carrying out the process as applied to theproduction ofsalicylic acid, but the details of the method are sub- Speeification of Letters Tatenti;

PoMrLIo, 4

plates from a cover or, support.

I have,

ject to variation and t e'jscale on which the process is worked wou d determine to some extent the actual steps which aretaken Three to. fivejparts by weight of caustic soda wit-none part of water are mixed in an electrolytic tank or cell and heated to about 110-120 (1' One 'part:of the.

o-cresol (85 to 95 per cent. o-cresol) is then added in small quantities with constant-agL tatlon. A voluminous vwhite mass of'sodiu-m cresylate is formed and the temp ature is then raised to about 230235 C. andthe- 'filled. The electrodes are then, introduced into the tank or cell (which may itself form an electrode), a convenient arrangement be. ing to suspend alternate anodesand cathodes in the form of vertical perforated The current is then passed between the electrodes at a constant anodic current densityof about '5 to 8 a-mperes per square decimeter, while the'heatingof the cell is so regulated as to keep the temperature during the. electrolytic action at about 240 to"2509; large scale work external heating may not be necessary but on a'smaller' scale the ternper-ature may be maintained by external means. It is desirable during the GlGCtl'OlY-t sis to pass some steam through the fused mass by means of iron'pipes extending'into the cell, in order to prevent packing of the material near the electrodes and to replace the water lost by evaporation and electrolysls.

After about a quarter to a half of the current theoretically required for conversion has passed (about 1 .5 ampere hours vper gram of cresol is the'theoretical quantity necessary) frothing starts and gradually increases in intensity. The material should be stirred to reduce this action, which disappears after about three quarters of the aforesaid theoretical current has passed, the material then becoming more viscous. At

this stage the steam supply should be in- I creased and the temperature carefully watched to avoid undue rise. It is found I as i by neutralizing the solution with an inexthat the conversion is practically finished when about one-half of the theoretical current haspassed.

The larger proportion of soda mentioned (about 5 parts) is usually preferable and although 3 to 4.50 parts give good yields the electrode. voltage is higher during the last stage ofelectrolysis. Still smaller proportions of thealkali, however can be em ployed if sufiicient provision is made to prevent the packing of the fused mass, for exmaterial.

ample by mixing some material capable of acting as a flux such as caustic potash with the caustic soda, if the latter is employed,-v or by the addition of salts (such as borates or acetates) which aid in the fusion of the ploycd, either wholly or mainly, the proportion necessary maybe greatly reduced as compared with the example given for caustic soda; for instance, betweenone and two' parts may be used to one'part of cresol. The process is applicable equally to the oecresol and to impure commercial cresols, which are ortho, meta) and para mixtures the final product resulting in mixed voxybenzoic acid salts that can be more readily separated than the corresponding cresqls and are of greater industrial importance.

The excess alkali can lie-recovered, for example, by dissolving the product of electrolysis in a small quantity of water and a passing carbonic acid gas through the solution to separate the alkali as a carbonate.

The salicylic acid can then be precipitated pensive commercial acid product, such as niter cake, and by completing the preclpitation by the addition of sulfuric or hydrochloric acid. Or the salicylate may be partly Also, if caustic potash is emcrystallized out by dissolvingthe product of electrolysis in hot water and allowing the solution to cool.

What I claim is: 1. A process for the oxidation of cresols,

in which a fused mixture of cresol and caus tic alkali is subjected to electrolysis.

2. A process for the production of salicylic acid or its salts, in which a fused mixture of o-cresol and caustic alkali is subjected to electrolysis.

3. An electrolytic process for the oxidain which a fused mixture of cresol and caustic alkali is subjected to electrolysis, water is added to the resulting product and carbon di-oxid passed therethrough to convert the alkali therein into carbonate, and the oxidized product precipitated by a suitable reagent.

In testimony that I claim the foregoing as my invention, I have signed my name.

UMBERTO POMILIO.

lVitnesses:

- FERRUCCIO JACOBEM LUGGERE,

GUISEPPE DIDO. 

